Logic modules of electronic devices, such as integrated circuit devices, typically employ a reference voltage that determines the high-level voltage representing a logic level at the module. When logic modules that have different reference voltages need to communicate with each other, a level shifter can provide an interface between the modules having different voltage references. The use of a level shifter allows a module having a lower voltage reference, referred to as a low-reference module, to interface with a module having a higher voltage reference, referred to as a high-reference module. The level shifter translates the lower voltage signal from the low-reference module to a higher voltage signal having a magnitude sufficient to represent the appropriate logic state at the high reference module. The level shifter can also translate signals from the high reference module to signals representing the appropriate logic state at the low-voltage module.
An exemplary prior art level shifter 100 is illustrated in FIG. 1. As illustrated, the level shifter 100 includes p-type transistors 102 and 104 and n-type transistors 106 and 108. The level shifter 100 is being driven by complementary input signals VIN and VINBAR of the low-reference module, where both of the complementary signals are at a voltage VDDL, which represents a high-level logic voltage reference that is lower than the high-level logic voltage reference, VDDH, of the high-reference module. However, the level shifter 100 can be unreliable when the input VIN transitions from one logic state to another. For example, as the input VIN transitions both the transistor 102 and the transistor 106 can be conductive simultaneously, and can remain so until the voltage at the shared node between them becomes low enough so that the transistor 104 becomes conductive. However, if the transistor 106 is not large enough, relative to the size of transistor 102, the signal VOUT may not transition to the desired high-level logic state in response to the logic state of the low reference module transitioning. Thus, the input signal VIN will not be appropriately translated at the high-reference module. Accordingly, there is a need for an improved level shifter device.